1. Field of the Invention
The present invention relates to cylinder locks, and more particularly to an improved cylinder security lock having conventional locking tumblers and secondary locking structure that operates independently of the tumblers. The secondary locking structure prevents operation of the cylinder lock until a properly configured key is placed in the keyway of the cylinder lock. The invention also relates to a novel key for operating the cylinder lock of the present invention.
2. Description of the Prior Art
Cylinder locks for locking doors, cabinets and other structures are well known in the art. These prior art cylinder locks typically include a cylinder shell, a cylinder plug rotatably received within the shell, and a plurality of tumblers reciprocally mounted in chambers extending through the shell and plug. The cylinder plug is typically coupled with a lock actuator that rotates with the plug for unlocking a locking mechanism such as a dead bolt upon rotation of the plug.
In more detail, cylinder plugs include a keyway for receiving a key blade. The tumblers are configured for preventing rotation of the cylinder plug until a properly configured key blade is inserted in the keyway. A properly configured key displaces the tumblers to a position that permits the rotation of the cylinder plug in the shell.
Although prior art cylinder locks effectively provide security when first installed, they can be circumvented shortly thereafter by unauthorized key duplication. Although it is common for companies to attempt to control access to a locked area by distributing only one key to each of their selected employees, the employees often have their keys copied by a locksmith. Thus, it is virtually impossible to control the distribution of keys that fit a particular lock since many extra keys can be cut without the knowledge or permission of the employer.
In an attempt to prevent unauthorized key duplication, many lock manufacturers repeatedly create new key blank designs and regulate the manufacture and distribution of the key blanks. However, due to the strong demand for key duplication services, locksmiths and key blank manufacturers usually gain access to these new blank designs and introduce copies of the blanks within a short time of their creation.
Another concern of lock manufacturers are the limitations in the amount of different key combinations available with any particular lock design. A common method of increasing key combinations is to produce locks and keys with different key blade shapes that are non-interchangeable thus increasing the number of useable different keys with essentially the same basic lock design. However, these keys still offer no protection against unauthorized key duplication.